/*
** $Id: lstring.c,v 2.8.1.1 2007/12/27 13:02:25 roberto Exp $
** String table (keeps all strings handled by Lua)
** See Copyright Notice in lua.h
*/


#include <string.h>

#define lstring_c
#define LUA_CORE

#include "lua.h"

#include "lmem.h"
#include "lobject.h"
#include "lstate.h"
#include "lstring.h"

#define LUAS_READONLY_STRING      1
#define LUAS_REGULAR_STRING       0

void luaS_resize(lua_State *L, int newsize)
{
    stringtable *tb;
    int i;
    tb = &G(L)->strt;
    if (luaC_sweepstrgc(L) || newsize == tb->size || is_resizing_strings_gc(L))
        return;  /* cannot resize during GC traverse or doesn't need to be resized */
    set_resizing_strings_gc(L);
    if (newsize > tb->size)
    {
        luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *);
        for (i = tb->size; i < newsize; i++) tb->hash[i] = NULL;
    }
    /* rehash */
    for (i = 0; i < tb->size; i++)
    {
        GCObject *p = tb->hash[i];
        tb->hash[i] = NULL;
        while (p)    /* for each node in the list */
        {
            GCObject *next = p->gch.next;  /* save next */
            unsigned int h = gco2ts(p)->hash;
            int h1 = lmod(h, newsize);  /* new position */
            lua_assert(cast_int(h % newsize) == lmod(h, newsize));
            p->gch.next = tb->hash[h1];  /* chain it */
            tb->hash[h1] = p;
            p = next;
        }
    }
    if (newsize < tb->size)
        luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *);
    tb->size = newsize;
    unset_resizing_strings_gc(L);
}

static TString *newlstr(lua_State *L, const char *str, size_t l,
                        unsigned int h, int readonly)
{
    TString *ts;
    stringtable *tb;
    if (l + 1 > (MAX_SIZET - sizeof(TString)) / sizeof(char))
        luaM_toobig(L);
    tb = &G(L)->strt;
    if ((tb->nuse + 1) > cast(lu_int32, tb->size) && tb->size <= MAX_INT / 2)
        luaS_resize(L, tb->size * 2); /* too crowded */
    ts = cast(TString *, luaM_malloc(L, readonly ? sizeof(char **) + sizeof(TString) : (l + 1) * sizeof(char) + sizeof(TString)));
    ts->tsv.len = l;
    ts->tsv.hash = h;
    ts->tsv.marked = luaC_white(G(L));
    ts->tsv.tt = LUA_TSTRING;
    if (!readonly)
    {
        memcpy(ts + 1, str, l * sizeof(char));
        ((char *)(ts + 1))[l] = '\0'; /* ending 0 */
    }
    else
    {
        *(char **)(ts + 1) = (char *)str;
        luaS_readonly(ts);
    }
    h = lmod(h, tb->size);
    ts->tsv.next = tb->hash[h];  /* chain new entry */
    tb->hash[h] = obj2gco(ts);
    tb->nuse++;
    return ts;
}


static TString *luaS_newlstr_helper(lua_State *L, const char *str, size_t l, int readonly)
{
    GCObject *o;
    unsigned int h = cast(unsigned int, l);  /* seed */
    size_t step = (l >> 5) + 1; /* if string is too long, don't hash all its chars */
    size_t l1;
    for (l1 = l; l1 >= step; l1 -= step) /* compute hash */
        h = h ^ ((h << 5) + (h >> 2) + cast(unsigned char, str[l1 - 1]));
    for (o = G(L)->strt.hash[lmod(h, G(L)->strt.size)];
            o != NULL;
            o = o->gch.next)
    {
        TString *ts = rawgco2ts(o);
        if (ts->tsv.len == l && (memcmp(str, getstr(ts), l) == 0))
        {
            /* string may be dead */
            if (isdead(G(L), o)) changewhite(o);
            return ts;
        }
    }
    return newlstr(L, str, l, h, readonly);  /* not found */
}

static int lua_is_ptr_in_ro_area(const char *p)
{
#ifdef LUA_CROSS_COMPILER
    return 0;
#else

#include "compiler.h"

    return p >= RODATA_START_ADDRESS && p <= RODATA_END_ADDRESS;
#endif
}

TString *luaS_newlstr(lua_State *L, const char *str, size_t l)
{
    // If the pointer is in a read-only memory and the string is at least 4 chars in length,
    // create it as a read-only string instead
    if (lua_is_ptr_in_ro_area(str) && l + 1 > sizeof(char **) && l == strlen(str))
        return luaS_newlstr_helper(L, str, l, LUAS_READONLY_STRING);
    else
        return luaS_newlstr_helper(L, str, l, LUAS_REGULAR_STRING);
}


LUAI_FUNC TString *luaS_newrolstr(lua_State *L, const char *str, size_t l)
{
    if (l + 1 > sizeof(char **) && l == strlen(str))
        return luaS_newlstr_helper(L, str, l, LUAS_READONLY_STRING);
    else // no point in creating a RO string, as it would actually be larger
        return luaS_newlstr_helper(L, str, l, LUAS_REGULAR_STRING);
}


Udata *luaS_newudata(lua_State *L, size_t s, Table *e)
{
    Udata *u;
    if (s > MAX_SIZET - sizeof(Udata))
        luaM_toobig(L);
    u = cast(Udata *, luaM_malloc(L, s + sizeof(Udata)));
    u->uv.marked = luaC_white(G(L));  /* is not finalized */
    u->uv.tt = LUA_TUSERDATA;
    u->uv.len = s;
    u->uv.metatable = NULL;
    u->uv.env = e;
    /* chain it on udata list (after main thread) */
    u->uv.next = G(L)->mainthread->next;
    G(L)->mainthread->next = obj2gco(u);
    return u;
}

